SELECTED QUARTERLY FINANCIAL DATA Selected Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 121,617	$ 118,108	$ 113,591	$ 103,405	$ 100,314	$ 108,136	$ 113,067	$ 101,227	$ 456,721	$ 422,744	$ 463,197
Gross margin	48,733	47,245	48,326	42,432	42,774	43,542	46,839	41,262	186,736	174,417	187,710
Operating income (loss)	(1,174)	(101)	2,277	(725)	(671)	(786)	(2,425)	(3,705)	277	(7,587)	3,241
Income (Loss) from Continuing Operations	(2,018)	(832)	1,279	(1,349)	(108)	(1,908)	(3,347)	(3,570)	(2,920)	(8,933)	1,607
Income (Loss) from Discontinued Operations, Net of Taxes	13	(16)	(53)	35	(184)	35	209	83	(21)	143	722
Net income (loss)	$ (2,005)	$ (848)	$ 1,226	$ (1,314)	$ (292)	$ (1,873)	$ (3,138)	$ (3,487)	$ (2,941)	$ (8,790)	$ 2,329
Earnings (loss) per share from continuing operations, basic and diluted	$ (0.06)	$ (0.03)	$ 0.04	$ (0.04)	$ 0.00	$ (0.06)	$ (0.10)	$ (0.10)	$ (0.09)	$ (0.27)	$ 0.05
Earnings (loss) per share from discontinued operations, basic and diluted	0.00	0.00	0.00	0.00	(0.01)	0.00	0.01	0.00	0.00	0.01	0.02
Earnings Per Share, Basic and Diluted	$ (0.06)	$ (0.03)	$ 0.04	$ (0.04)	$ (0.01)	$ (0.06)	$ (0.09)	$ (0.10)	$ (0.09)	$ (0.26)	$ 0.07
Weighted Average Number of Shares Outstanding, Basic	32,063,000	32,151,000	32,048,000	32,161,000	32,227,000	33,572,000	33,252,000	34,631,000	32,106,000	33,174,000	33,869,000
Weighted-average common stock outstanding - diluted (in shares)									32,106,000	33,174,000	34,084,000
Common stock equivalents and outstanding stock options excluded from the calculation of diluted earnings (loss) per share (in thousands)	1,189,000	1,189,000	1,189,000	1,089,000	604,000	299,000	548,000	1,345,000	1,188,933	603,500	556,000